This article describes a device for the reduction
of intra-abdominal pressure. The device (ABDOPRE) includes a unique external
servo-control mechanism, based on urinary bladder pressure measurement. The
results of ABDOPRE use in the first four intra-abdominal hypertension patients
are reported; the device resulted in a reduction of intra-abdominal pressure
between 16% and 35% in 3 cases and in a paradoxical increase of the intra-abdominal
pressure in an obese woman, likely due to inappropriate chamber size for the
patient's anatomy. These results are promising and ABDOPRE may be useful in
clinical practice.

Intra-abdominal hypertension (IAH) and abdominal
compartment syndrome (ACS) are frequent in critically ill patients and are independently
associated with increased morbidity and mortality.(1) Intra-abdominal
pressures (IAP) above 20 mmHg have a negative impact on both intra- and extra-abdominal
organ perfusion.(2) This manuscript reports on a prototype device
(ABDOPRE) able to generate a negative pressure over the patient's abdomen, aimed
to reduce the IAP; it additionally reports on the preliminary medical experiences
with this device. This device is proposed to provide controlled reduction of
the IAP.

Since 2006, the Department of Intensive Care
Medicine and the Biomedical Engineering group have been cooperating to build
a device  called ABDOPRE  able to accomplish the proposed objectives (Figures
1, 2 and 3).(3) ABDOPRE
is comprised of the following: 1) a vacuum pump (150 mmHg pressure, maximal
flow 0.4 L/min, fed by a 6-Volt source and with 65 dB noise) plus connections;
2) a rigid and transparent chamber, adjustable to the skin; and 3) a pressure
data acquisition and automated control system (servo-controlled) and a user's
interface screen.(3) The IAP was continuously measured according
to Balogh's(4) technique, using a 3-way intravesical catheter, keeping
the urine output independent. The ABDOPRE software allows maintenance of the
hypotensive therapy schedule. The ABDOPRE scan concomitantly displays the IAP
and therapeutic target, allowing physicians to monitor both the device performance
and patients' IAP. In contrast to the model described by Valenza et al.,(5)
ABDOPRE has a servo-controlled pressure system, which uses the intravesical
pressure as a control variable.

Informed consent was obtained from a patient's
relative. The investigators played the role of healthy volunteers. The institution's
Ethics Committee approved this study protocol.

CASES

The initial assay was conducted on a healthy
volunteer achieving a -90-mmHg chamber pressure. During progressive negative
pressures, the subject experienced considerable abdominal expansion. From -30
mmHg on, the subject reported some abdominal wall discomfort due to stretching;
therefore, the test was discontinued. The test duration was 3 minutes. Upon
completion of the test, the subject had an erythema on the chamber contact area.

ABDOPRE was tested in 4 patients: 2 female and
2 male. The mean age was 48.5 years (ranging from 18 to 78 years) (Table
1). Mean body weight was 74 Kg, and the mean APACHE II score was 22. The
IAP was measured as millimeters of mercury (mmHg). All 4 patients had Grade
I IAH. In 2 patients, the IAP dropped to 9 mmHg, with a delta intra-abdominal
pressure (ΔIAP = IAPinitial  IAPfinal) of -5 mmHg and -3 mmHg, respectively.
Another patient displayed a drop from 12 mmHg to 10 mmHg, ΔIAP = -2 mmHg.
The mean percent change was -25.3% (range 16-35%). In one patient, the IAP was
increased by 38% over the baseline. This finding was an obese female patient
(95 Kg) with a 34.9 body mass index (BMI) for whom the chamber was too small.
This increased IAP was likely explainable by a 'ventosa effect', developed due
to the inadequate proportion between the glass chamber and the abdominal wall.
Therefore, the intra-abdominal volume was reduced due to intromission of part
of the abdominal wall into the chamber; additionally, perhaps the chamber plus
part of the abdominal wall represented an increased weight over the abdomen,
resulting in this paradoxical effect on the IAP.

IAP reductions were obtained for all patients
with -35 mmHg pressures, with the target achieved within the proposed time (10
minutes) and maintained for about 1 hour. No changes in mean blood pressure
or heart rate were observed, and no arrhythmia was identified. The procedure
was well tolerated, with no discomfort observed and no ventilator issue ascribable
to pain. All patients were sedated (midazolam 0.083 mg/Kg/hour) and under analgesia
(fentanyl 3 mcg/Kg/hour) as continuous infusion.

COMMENTS

This article reports on a preliminary trial with
a small number of cases. The performance of the device was acceptable and safe.
In 3 of the 4 patients, IAP was reduced by about 25%. The fourth case had a
paradoxical increase; the likely explanation was addressed earlier in this paper.
This failure led to a chamber review; consequently, its diameter was increased
to prevent this paradoxical effect. The initial prototype (Figure
2) would be inconvenient for obese patients. However, this should be considered
as a developing device that remains to be improved. Its use according to appropriate
research protocols will allow optimization of its performance and the user's
interface and may potentially provide a clinical tool for the management of
IAH.